The present invention relates generally to coolant systems for cooling an engine in a vehicle.
Engine coolant pumps (also called water pumps) are employed to pump a coolant through the engine to cool the engine and pump coolant through a heater core to provide heat to a vehicle passenger compartment. These pumps are conventionally driven off of the engine, so they pump continuously when the engine is on. Moreover, the speed of these engine driven coolant pumps is based on the speed of the engine. This method of operating the pump does not lead to the most fuel efficient vehicle operation.
In order to improve the vehicle fuel economy, then, some have replaced a conventional engine driven coolant pump with a coolant pump that is driven by an electric motor. This allows the speed of the pump to be varied according to the amount of coolant flow needed at any particular time to meet vehicle thermal requirements. However, relatively high electric loads and large, expensive electrically driven pumps are sometimes required to meet the peak demand for coolant flow. This high electric load and expensive, large, electrically driven pump is undesirable for some vehicles. Accordingly, it is desirable to meet engine cooling and passenger compartment warming needs while maximizing vehicle fuel economy and minimizing peak electric loads needed for pumping coolant.